Multi-threaded IO performance regression on 2.6 kernel?

[Xie, Bill]

All,

I am testing the multi-threaded IO performance on Opteron servers. 

I use dd as the test tools. The single dd can reach 60MBps for single disk.

on 2.6.5 kernel, If dd numbers exceed the CPU numbers, vmstat bi reduced to 20MBps.

on 2.4.21 kernel, multi-threaded IO performance works fine, even I run 40 dd command at same time.

Does anybody experienced similar issue also?

Best Regards
Bill Xie

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